A gal who has done extensive studying of tree crickets (including song analysis, mating trials, and DNA sequencing) once wrote to me: In the eastern United States, I have found O. nigricornis, but not O. forbesi (in NJ and three sites in NY). In Ohio, I have found both O. forbesi and O. nigricornis in the same field, although the sites where I have found this have been in eastern Ohio (Akron and Canton). In central Ohio (Columbus area) and west from there, I have found O. forbesi but not O. nigricornis (OH, IL, WI, MI, IN, SD).

This is the range I'm going to go by for now in separating the two species. Anything in the states of OH, IL, WI, MI, IN, SD should go in the nigricornis vs forbesi taxon page.

However, anything clearly beyond this area in any given direction, i.e. north of New York, should probably be placed in the species that matches her comments above. i.e. I feel it's wise to surmise that O. forbesi is most likely not found in Maine.